1. Field of the Invention
The invention relates to a method for ensuring the reliability of technical components, especially of internal combustion engines and the parts thereof, by means of a test program.
2. The Prior Art
Vehicle owners expect that each new generation of engines offers higher performance, lower fuel consumption and reduced emissions in combination with the highest reliability. At the same time, the vehicle manufacturers urge shorter development periods. In this field of tension, ensuring reliability during the development process is of special importance.
It is known from the publication “Der AVL-Reliability-Engineering-Prozess für die Motor-und Antriebsstrangentwicklung” (The AVL reliability engineering process for the development of engines and drive train), Klaus DENKMAYR, VDI-Berichte 1713, 2002, pages 27 through 32, to illustrate the damage of units, components and modules in a load matrix. Different engine properties can be tested by means of test programs, especially different endurance test runs, with different engine subsystems being loaded in highly different ways. For example, in a thermal shock test the cylinder head is highly loaded, whereas the crankshaft is loaded to a lesser extent. In order to outline the different loads and discover possible weak points in the test program, the so-called load matrix was introduced in this publication. The load matrix states the amount to which the respective endurance run of the subsystems provides a load in comparison with the typical use during the normal service life.
The B10 service life is usually used as the reliability index for internal combustion engines, which service life states the running output until 10% of the total population of a group of engines shows a serious defect. Depending on the application, the B10 value is stated in kilometers, miles or hours of operation.
A further important reliability parameter is the so-called repair frequency which states the frequency of defects of components or modules per year of warranty. The reliability parameters of B10 service life and repair frequency have a relevant influence on the costs by warranty and gratuitous services for the makers of engines and vehicles. Shorter development periods, harder utilization profiles and rising warranty and accommodation periods lead to the consequence that ensuring reliability in components and modules is rising in importance.